This invention relates to a test plug, and more specifically to a test plug for sealing an internal passageway of a vessel preparatory to pressure testing the vessel with a fluid, either a liquid or gas. This invention is particularly well suited for use in testing, from ground level, vessels such as gasoline tanks, that are installed beneath ground level. Specifically, the test plug of this invention can be used to carry out such tests without in any way disturbing the underground piping connections to these vessels.
Reference throughout this application to "vessels," unless indicated to the contrary, is intended to cover all types of devices including an interior area that is intended to be sealed preparatory to carrying out either hydrostatic or pneumatic internal pressure tests. For example, the vessels can be tanks, pipelines, boilers, as well as other structures having an interior area to be tested, as indicated above.
It is often desirable to periodically pressure test vessels to determine whether the connections, seams, rivets or other fastening means will continue to hold a preselected pressure without leaking. This is particularly important in vessels that are intended to carry, or store highly flammable materials such as gasoline.
When carrying out a pressure test of gasoline tanks, it is necessary to temporarily seal the various passageways that communicate with the tank interior, and introduce a fluid under pressure through one of these passageways. A pressure gauge generally is employed in the line through which the pressurizing fluid is introduced so that the pressure test can be carried out at the desired preselected pressure level. When the passageway to be temporarily sealed is internally threaded, it is highly desirable, if not mandatory, to employ an externally threaded seal member as a part of the test plug assembly. Also, when the tank is installed underground, it is important to be able to insert and actuate the test plug from ground level without disturbing the tank piping connections and without excavation. It is believed to be most desirable to form the test plug with a compressible sealing gasket, preferably in the form of a conventional O-ring, that is forced into sealing engagement with the interior surface of the vessel passageway when the plug is actuated. The greatest versatility is achieved by designing the plug so that it can be inserted into a vessel passageway and actuated to perform its sealing function in separate operations.
Many different types of test plugs are known in the prior art, as exemplified by the disclosures in U.S. Pat. Nos. 2,636,514 (Woodward); 1,644,118 (Florence); 3,483,894 (Finocchiaro) and 2,886,067 (Maxwell et al). However, these devices are deficient in one or more ways in meeting the objectives of this invention.
In the Woodward test plug, the annular sealing gasket seats against the upper wall of the passageway, not against an interior wall as is preferred in this invention. Moreover, the operation of inserting the device into the passageway also forces the gasket into its sealing position. The steps of inserting the device and actuating the gasket cannot be separated.
The Florence and Finocchiaro test plugs are not suitably designed for sealing an internally threaded passageway of a vessel; particularly because neither includes an externally threaded member that can cooperate with the internal threads. Furthermore, both of these test plugs are designed to use specially designed sealing rings including internally tapered surfaces. They would not function as well as with conventionally formed O-rings of the type that are usable in this invention.
The Maxwell et al test device, like the Florence and Finocchiaro devices, is not designed for sealing an internally threaded passageway of a vessel. The Maxwell device includes elements that must cooperate with the exterior surface of the vessel in order for the sealing operation to be carried out.
None of the above devices is particularly designed for the pressure testing of vessels installed below ground level.